The invention is related to polyesters and to methods for making the same and is especially related to such polyesters which are useful as electrical insulation. More particularly, this invention relates to aliphatic isocyanurate modified polyesters and to methods for producing the same and to aliphatic isocyanurate modified polyesters applied as magnet wire insulation.
Tris(2-hydroxyethyl)isocyanurate containing polyesters have been widely used as magnet wire coatings, for example as a base coat under a top coat of a different material. Tris(2-hydroxyethyl)isocyanurate (THEIC) produced separately has been added as a reactant in the polyesterification reaction of the polyesters.
THEIC and other aliphatic isocyanurates have been produced by a variety of methods. THEIC has been produced by reacting cyanuric acid with ethylene oxide and by reacting cyanuric acid with ethylene carbonate. Triglycidyl isocyanurate has been produced by reacting cyanuric acid with epichlorohydrin and by reacting cyanuric acid with glycidol. Tris(2-hydroxypropyl)isocyanurate has been produced by reacting cyanuric acid with propylene oxide. Tris(hydroxymethyl)isocyanurate has been produced by reacting cyanuric acid with formaldehyde. Tris(2-hydroxypropyl) isocyanurate has been produced by reacting cyanuric acid with propylene carbonate.
Aliphatic isocyanurate containing polyesters have alternatively been produced by reacting cyanuric acid with ethylene carbonate in situ with dimethyl terephthalate to produce THEIC polyester and with other components to produce THEIC containing polyester-imides and polyester-amide-imides.
The former procedures for producing the alphatic isocyanurate containing polyesters have the shortcoming of requiring the isocyanurate as a reactant. The latter procedures have the shortcoming that both ethylene carbonate and ethylene oxide react with conventional phenolic solvents such as cresylic acid, phenols, cresols and the like and thus polar, aprotic solvents must be used.
Conventional phenolic solvents, as opposed to polar, aprotic solvents, are preferred in the production of magnet wire for reasons of both utility and cost.
In addition, polar, aprotic solvents can present difficulties in the application of even, consistent, smooth coatings on certain substrates, such as fine wire or base insulation materials or substrates subject to attack by the solvents. Problems have also been experienced in using such solvents with conventional magnet wire towers, because of the extremely high temperatures, which are necessary to expel such solvents from coatings and their tendency to autoignite at such temperatures.
It is therefore highly desirable to provide improved aliphatic isocyanurate containing polyester resins and improved methods for producing the same and improved magnet wire having magnet wire insulation including improved aliphatic isocyanurate containing polyester resins and an improved electomagnetic device.
It is also highly desireable to provide such improved resins and improved methods and improved magnet wire and improved electromagnetic device from reaction solutions having, as a cosolvent, conventional phenolic solvents.
It is also highly desireable to provide such improved resins and improved methods and improved magnet wire and electromagnetic devices, in which such resins are polymerized to useful molecular weight in solvents of moderate polarity.
It is also highly desirable to provide such improved resins and improved methods and improved magnet wire, in which such resins can be provided in solutions having relatively low viscosities and relatively high resin contents.
It is also highly desirable to provide such improved resins and improved methods and improved magnet wire and improved electromagnetic devices in which chemical and electrical properties are acceptably similar to those of conventional polyester resins modified with Tris(2-hydroxyethyl)isocyanurate.
It is finally desirable to provide such improved resins and improved methods and improved magnet wire and improved electromagnetic devices, which have all of the above desired features.